HC blend and oil return

First I want to thank everyone for the help you have given in the past.
Here is my concern: I am working on an ice-bank water chiller that was operating on 134a, I have flushed the system replaced the dryer, expansion valve as well, The compressor I am using was filled with alkybenzene oil (it had 16 ounces of oil n it. I have read the oil is compatible with the HC blend. When I pulled the old 134a compressor I poured out about 5 ounces of old oil (it wasn't in the evaporator or the accumulators ad since it is a sealed system I can only surmize it was shipped with the low level oil. apparently the POE oil and 134a doesn't move through the system.
Here is my main concern, if I add about 20 ounces of the alkybenzene to the 'new' compressor will it move through the system okay so it won't starve the compressor?
What about adding some kind of oil separator if you guys think I will have oil return issues?
Thanks in advance for your all your help!